The disclosed technology relates to a lubricant for a sump-lubricated internal combustion engine.
There is a continuing desire to provide lubricants for internal combustion engines with reduced phosphorus content or reduced metal content as measured by sulfated ash (ASTM D 874). This desire is largely motivated by the fact that, while such materials may be quite useful in the lubricant, they may, in a similar manner, make their way into the exhaust stream. Phosphorus and metals in the exhaust, in turn, are believed to interfere with pollution control devices such as exhaust catalyst systems or particulate filters.
Conventional lubricants, with comparatively high levels of additives that contribute phosphorus or metal as measured by sulfated ash, can typically exhibit good lubricant performance. However, current or future lubricants containing lower levels of phosphorus (e.g., <0.06%) and sulfated ash (e.g., <0.80%) can be more difficult to formulate so as to provide adequate performance.
Polyethers of various types have been used in a variety of lubricant and fuel formulations. For instance, U.S. Pat. No. 5,652,204, Cracknell et al., Jul. 29, 1997, discloses lubricating oil compositions for automotive engines containing certain end-capped polyethers. The polyether may comprise from 0.1 to 99%, most preferably from 5 to 25% by weight of the composition.
U.S. Pat. No. 6,596,674, Botz, Jul. 22, 2003, discloses metal working lubricants comprising a primary lubricity component such as a polyether or polyether ester. The primary lubricity component may comprise from about 0.05 to about 5 percent by weight of the liquid composition of matter. The liquid composition of matter may include a diluent which may comprise water.
U.S. Pat. No. 6,136,052, Daly, Oct. 24, 2000, discloses fuel additives comprising a polyether alcohol. Certain formulations of gasoline contain 50 to 300 ppm of polyether fluidizer.
U.S. Publication 2009/0156446, McAtee, Jun. 18, 2009, discloses a lubricating composition, particularly for an internal combustion engine, which includes an antiwear agent which may comprise a polyhydric alcohol with mono-meric units of oxyalkylene groups.
PCT Publication WO 2010/048137, Apr. 29, 2010, discloses reduction of high-aqueous content sludge in a sump lubricated diesel engine, lubricated with a certain lubricating formulation, by including in the lubricant a polyalkylene oxide.
We have now found that certain components, in particular, polyethers (such as polyether fluidizers) normally have little or no effect, or even a negative effect, on lubricant stability when used in conventional lubricants but have beneficial effects when used in low-phosphorus and optionally low-ash formulations.